Tags track cuckoos on route south

Cuckoo wearing a satellite tracker
Cuckoo wearing a satellite tracker
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THE disappearance of our cuckoos is being investigated with the help of new technology.

The British Trust for Ornithology, based at a former nunnery in Thetford, is using a new generation of satellite trackers, at £2,500 each, to see where cuckoos go when they leave here. Their numbers have halved in 25 years making them our fastest declining migrant.

Though satellite tracking has long been used on large birds, a BTO spokesman said that until now they were not small enough to use on cuckoos, which are about the size of a town pigeon. To avoid welfare problems, devices can only be attached to a bird if they weigh less than five per cent of its body weight.

The BTO spokesman said: “These weigh five grams and we’ve not put them on cuckoos weighing less than 115gm.”

The five tagged cuckoos are all from Norfolk and are males because they are larger and are easily trapped by playing cuckoo calls. All are named after people connected with the project.

The tags have already revealed surprises. Clement, named after BTO director Andy Clement, and Chris, named after Springwatch presenter Chris Packham, left earlier than expected. Clement was in Thetford last Thursday but by Sunday was 100 miles south of Paris. Chris left Mundford a day later and was in Sussex on Sunday.

Track them at www.bto.org.uk